A variety of procedures are available to treat low-back pain, but, with few exceptions, it is not known which patients are most likely to benefit from which treatment and under what circumstances. For chronic low back conditions, there is even less consensus regarding the most appropriate method of treatment. With little scientific evidence to support one therapeutic modality over another, treatment decisions are often made on the basis of personal observation and practice style. As a result, patients may receive less than optimal care, and there may be significant economy consequences in the form of resource allocation and indirect cost impact. This study embraces an interdisciplinary approach in an effort to address the complex issue of variations in health care delivery and patient outcomes for ambulatory low back conditions. The objectives of this project are to: describe and quantify condition-specific and general health outcomes for MD and DC patients; identify those practice activities associated with the most favorable and least favorable outcomes for specific patient profiles--defined in terms of low back history and chronicity of presentation; examine relationships between psychosocial, behavioral factors and patient outcomes and costs; and foster consensus building between chiropractors and other primary care physicians relative to low back patient management strategies. The research design is a longitudinal, prospective, practice-based study of non-randomized cohorts. One hundred eleven primary care medical physicians (MDs) and 60 chiropractors (DCs) will enroll a total of 4,352 patients into the study over a period of 12 months, and patient outcomes will be systematically assessed during a 12 month follow-up period.